1. College of Materials; Xiamen University; Simingnan-Road 422 Xiamen 361005 P. R. China
2. College of Optical and Electronic Technology; China Jiliang University; Hangzhou 310018 P. R. China
3. Sialon Group; Sialon Unit; National Institute for Materials Science; 1-1 Namiki Tsukuba Ibaraki 305-0044 Japan